RCExplorer Tricopter v2.5 FPV platform build

This is a build log of my RCExplorer-based FPV tricopter. Each phase is documented in a single post, with plenty of build pics, and there are related comments and dialog from other contributors throughout.

Recently I decided to do a build of David's (rcexplorer.com) version 2.5 tri. The simplicity and crash survivability of the design appealed to me, Plus I like its clean lines.

Here is the link to David's build log which I used extensively. http://rcexplorer.se/projects/tricop...copterv25.html. Note that there are important design and assembly elements tucked away in all of the version build logs he has there (1/1.5, 2, 2.5) and I recommend reading them all several times if you want to end up with an excellent build.

As to survivability, parts are designed to pop off or pivot when there is a crash, instead of breaking or bending electronic or power components. Worst case, one of the arms will break, which is a $1 part and easy to replace. And based on my Trex 450 track record, I will be crashing. So I decided it would be to my advantage to figure the crashes into the build :-)

I wanted to mirror Dave's parts list as precisely as possible, to minimize surprises...at least for this first tri build.

I bought most of the parts from Hobbyking, using David's shopping list (very helpful!), except where they were out of stock, as was the case for the 18 amp Turnigy plush ESCs, and the tail servo. I was able to find 25 amp Turnigys elsewhere (couldn't find any 18 amp Turnigys, so I scaled up). The tail servo I ended up using was a Turnigy TGY-930 from HK. I also used the HK KK controller board. And I picked up the CF rod at Hobbytown.

Here are all of the parts, or at least most of them, ready to experience life as a tri:

For the center frame, my friend (and all around great guy) Mike "crash" Hancock cut the G10 from plates I ordered from mcmaster-carr.com (9910T15 Multipurpose Garolite (G-10), 1/16" Thick, 12" X 12"). Mike's site has some really excellent video blogs and other resources on all kinds of RC stuff, including FPV and multicopters. He also scratch built the computer controlled cutting machine that cut my frame. Check out his site at http://allthingscrash.com/.

Here are the plates he cut from the G10 sheets, and the battery tray/gopro mounts from 1/8" basswood plywood. Note that there are two complete sets in this picture:

I started with the main frame components:

I made sure that the top and bottom G10 plates' holes and edges were perfectly aligned before I did anything else:

Then I cut the arms (I used 48 cm, like David), and rough assembled them with the frame pieces:

Time to put together the tail assembly, which was part of the process I really enjoyed. Drill out one of the two interlocking landing gear pieces, line up its hole with the other one, and jam the CF rod through both:

Sand down the ridge on the back of the servo arm (I ended up using a different arm, by the way):

Center and CA the horn to the assembly so that a couple of the screw holes line up with solid plastic for drilling holes, and let CA set:

Drill holes, screw horn to assembly and cut off any unneeded parts of the horn:

Zip tie the motor mount on, paying very close attention to the orientation and direction of each zip tie:

I had to diverge from David's build here because of the different servo dimensions. I added a piece of wood as a shim under the assembly so that the servo would line up with the horn hole on the assembly when both pieces were sitting on the tail arm. Here I have a couple of screws I'm about to tighten to clamp the two pieces together and let the CA between them set:

And here is a picture of all motor mounts affixed to the arms:

Here is the basic frame and motor mounts assembled and extended:

On to the motors...I epoxied (actually JB Welded...I hope the iron in the compound won't mess with the winds of the motor!) the wires, per Dave's suggestion, to minimize metal fatigue:

Cutting down the motor shafts. I cut mine to 22 cm:

I also had to relocate the servo wires exit point to another side, since they were coming out of the side that needs to be flush to the arm:

Here is the finished tail motor and servo mount:

And here are all three motors mounted:

Now it's time to work on the electronics. I decided to flash the HK KK board next. Staying as true to David's build as I could I used firmware v1.6 (even though later versions were available.) I couldn't get the Sparkfun.com Pocket AVR programmer to work with my mac (which they pointed out on the product page might be an issue), so I worked from Windows 7. I ran into problems and had to do the following to get everything to work:

I took a page out of the Food Network programs and used a bowl to collect all of the bits and pieces of trash as I worked:

And then I hovered it the living room! It just worked. Awesome. Here is a post-hover pic:

So that is all for chapter one: Build the tri and make it fly! I started Saturday afternoon, and worked most of the the weekend and Monday night to get it from parts to a flying machine. I figure around 25 hours of work to get it to this point.

Finished mine recently, one thing i changed was the UC. In true RCExplorer style i used massive cable/zip ties

Another more important thing i've done is add a 'front' to it for LOS flying before i add the fpv gear. I've noticed that many multicopter pilots seem to identify the tail, usually by painting it a bright colour. Personally i don't think this is a good idea as it may encourage the pilot to look for the tail during loss of orientation (which is very easy with a symetrical craft like a tri or quad). I remember back to my rc heli learning days, an experienced heli pilot said:

"Always look at the nose of the heli instead of the tail"

This helped massively with orientation as yaw left moves the nose left and yaw right moves the nose right. Now i know this sounds obvious but if you're concentrating on the tail, yaw left moves the tail right..... and before you know it you've 'bought the farm'.
This will not be an issue when flying fpv......... hope my new vtx turns up soon.

I had to cut my G10 sheet by hand but apart from that this build is identical.

Badlands: Wow...handcutting G10. That is impressive. Super nice vid. I have the dragon link, too. That will be going on this tri. Plus a gopro I'll pick up at some point.

Quote:

Finished mine recently, one thing i changed was the UC.

Crezzee: What is UC? I love how clean your build looks in the pic. I've been planning on doing a similar approach as you with the landing gear, but can't think of what I can use to cut the circles from. What did you use?

Where do you buy the wooden arms for Tricopter? Is it pine wood? It looks nice.

Hi tuongnhu. I got these at a Hobby Lobby store. They are basswood. 3/8" x 3/8" x 24". $1.49 each. I've heard that on long pieces, pine will often warp and bend. Apparently bass wood stays straighter. Whatever you use for your arms, use something that will stay true.

Crezzee: What is UC? I love how clean your build looks in the pic. I've been planning on doing a similar approach as you with the landing gear, but can't think of what I can use to cut the circles from. What did you use?

UC is Under Carriage and yes i use very big zip ties. So far they have worked great as they absorb some of my heavy landings.

Finished mine recently, one thing i changed was the UC. In true RCExplorer style i used massive cable/zip ties

Another more important thing i've done is add a 'front' to it for LOS flying before i add the fpv gear. I've noticed that many multicopter pilots seem to identify the tail, usually by painting it a bright colour. Personally i don't think this is a good idea as it may encourage the pilot to look for the tail during loss of orientation (which is very easy with a symetrical craft like a tri or quad). I remember back to my rc heli learning days, an experienced heli pilot said:

"Always look at the nose of the heli instead of the tail"

This helped massively with orientation as yaw left moves the nose left and yaw right moves the nose right. Now i know this sounds obvious but if you're concentrating on the tail, yaw left moves the tail right..... and before you know it you've 'bought the farm'.
This will not be an issue when flying fpv......... hope my new vtx turns up soon.

I learned to fly my tricopter by looking a the tail, first time I flew it FPV I nearly crashed when the rudder was "inverted". After landing and giving it another go flying visually I went like: "What's the matter with this thing? left stick, tail goes left, good; right stick, tail goes right, goo... waaaaaaait a second..." Facepalm

Awesome post and thread, thanks for the update and great to see it flying. What type of power are you at to get to a hover? I know David flys his FPV so I am assuming it can hoist a bit of weight, I've got two go pros and have been toying with the idea of how much fun this thing would be carrying two of them in the 3D set-up...